Cannabis plants can’t vocalise a call for help—but they can send signals to tell you all is not well. If you see leaves either clawing or curling, there is trouble with the trees. Don’t ignore their pleas. This blog will help you identify the causes and cures for curly cannabis leaves.
Indoor growers must constantly maintain the optimal environmental conditions. This starts with optimal light distance. The only way to keep the plant canopy in the sweet spot is to measure and adjust until mature plants peak in height during mid-late bloom, depending on the strain. Moreover, indoor growers can utilise air-con and fans to keep the grow-op cool.
Genetics are the cause of all kinds of cannabis leaf deformities and mutations. Some strains occasionally have a tendency towards curly leaves or other odd traits. Most growers will thin out these plants. All the shrewd cultivator can do is write it off as bad luck.
Outdoor growers confronted with heat waves and drought conditions have less control than the indoor grower. Constructing a simple screen shade will keep plants slightly cooler and may prevent leaves from fraying and curling further. You can’t really revive scorched leaves and will have to remove older foliage beyond saving. Also, planting in white pots instead of black pots will keep the root zone cooler.
Heat stress can occur indoors or outdoors. If you see curling and nasty-looking brown fringing, your cannabis leaves are sending you a distress signal. Cannabis plants can photosynthesise efficiently at moderate temperatures up to 28°C. Anything above 30°C and your plants are in the danger zone. Combine this with low RH and you’ve got real problems. New leaves will grow gnarly and old leaves will curl yellow and maybe even burn to a rusty, brown crisp.
Cold temperatures can cause curly cannabis leaves too. Eventually, all kinds of leaf discolouration will develop. Sure, cooler nighttime temps late in bloom can add a dash of purple charm to buds, but prolonged exposure to temperatures below 10°C will kill your plants. Flowers will be loose and leafy if plants even make it to harvest. Coupled with high RH, buds will be moist and become vulnerable to Botrytis, AKA bud rot.
If you can’t lift the containers, then consider a moisture meter and make sure to carefully monitor post-watering plant behaviour. Try reducing the volume of water. Alternatively, take longer intervals between waterings. Unfortunately, Pythium is virtually incurable and will turn your plant’s roots into brown sludge. If you see droopy, curly cannabis leaves, especially with young plants, look to the roots for answers.
Dial in feeding. Easier said than done right? Wrong! Almost every brand of well-known cannabis fertiliser offers a feeding chart free to download from their respective websites. Granted, not all cannabis varieties will respond in the same way to fertilisers.
Overwatering will literally drown your plant’s roots. Excess water will not only rinse most of the beneficial microbes from the medium, a sodden substrate can also become colonised by algae and nasty fungi. Persistent overwatering invariably invites the parasitic Pythium, better known as root rot. Cannabis plants with droopy, claw-like leaves could be trying to tell you they are waterlogged.
Cannabis leaves curling or clawing are signs your plants are suffering. Something is going wrong in the garden. This blog will help you save the stash.
Only one of my 3 plants is having this issue.
You mentioned that this is happening to only some of your plants. If this is happening to the plants which are closest to your grow light, that’s a hint that the problem may be temperature related.
When growing with hot HID lights, good ventillation and an exhaust fan will go a long way towards preventing all these problems. If the whole grow area is too hot with stagnant air, you will want to consider venting out all that extra heat.
When the the serrated edges of marijuana leaves curls or tipped up like that, it’s often a sign of temperature stress, overwatering/root problems or extreme humidity levels. This plant was overwatered and living in high heat, which is what caused these symptoms.
If plants are also droopy, it’s likely you’re dealing with watering or root problems.
Any ideas of anything else I should check?
When the problem is low humidity, the leaf will also often fold in the middle, like a taco.
A friend suggestted that the issue may be low humidity.
Question: What do I do if the edges of my cannabis leaves are curling up?
[Answer inside!] Only one of my 3 plants is having this issue. A friend suggestted that the issue may be low humidity…